The United States has expressed "deep concern" about mob violence reportedly targeting international NGOs operating in Myanmar's restive west.

In a statement released Thursday, the U.S. Department of State highlighted what it viewed as "the continued lack of adequate security forces and rule of law on the ground in Sittwe," the capital of Rakhine state.

Rakhine, located along Myanmar's west coast, has been at the center of an ongoing sectarian conflict between Buddhists and Rohingya Muslims, which has seen hundreds of people killed and tens of thousands more made homeless.

Census controversy

An upcoming census planned by the central government has triggered further unrest amid fears it could exacerbate tensions between the state's majority Buddhist population and the Rohingya -- a stateless Muslim minority not recognized as citizens or one of the country's 135 "official" ethnic groups. Myanmar's government has come under increased pressure to take action to ease the unrest, and recently sent more troops to the region.

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Sectarian violence continues in Myanmar

The attacks this week in Sittwe, which targeted the offices and facilities of a number of international aid agencies working in the city, were triggered by reports that a foreign aid worker had treated a Buddhist flag disrespectfully.

The worker in question, a staffer with the Europe-based humanitarian group Malteser International, had removed the flag from its building. Many flags have been hung on buildings across the state ahead of the census as a sign of opposition to the Rohingya population -- who are widely viewed as intruders from across the border in Bangladesh.

In a statement posted on their website Friday, Ingo Radtke, Secretary General of Malteser International, wrote: "Malteser International is committed to the humanitarian principles and therefore the absolute ethnic and political neutrality of our work is our highest priority. We therefore avoid any form of political, religious or ethnic partisanship. That is the reason why our program coordinator has removed the Buddhist flag which -- in the local context -- might be seen as a symbol for a political positioning. She did not act in any degrading manner or express any cultural misconduct."

Aid groups 'bias'

But foreign aid groups have come under fire in Myanmar for allegedly showing bias towards the Rohingya. Last month, Medecins Sans Frontieres (Doctors Without Borders) was banned from operating in the volatile state following protests by ethnic Rakhine nationalists against the organization and other international NGOs.

Myanmar's government said the organization had been banned for consistently showing bias towards the state's Muslim minority and breaching the terms of its agreement to operate in Rakhine, where it provided services to tens of thousands of patients. MSF said it was "deeply shocked by this unilateral decision."

As the major NGO healthcare provider in Rakhine, it ran clinics in nine townships across the state, "treating anyone who was unable to access the medical care they required," including tens of thousands of vulnerable people who had been displaced into camps by recurrent communal violence.